Retinal implant for rare eye disease

The device, made by privately held Second Sight Medical Products Inc of Sylmar, California, consists of a special pair of glasses outfitted with a video camera and a video processing unit that sends signals to a wireless receiver implanted in the eye.

Called Argus II, the system is intended to replace the function of cells in the retina destroyed by retinitis pigmentosa, an inherited degenerative disease that affects about 100 000 people nationwide.

The retina, which is made up of light-sensitive tissue that lines the back of the inner eye, works a bit like film in a camera, converting images that come through the eye's lens into electronic signals that are relayed to the optic nerve in the brain.

The device does not completely restore vision

Although it does not completely restore vision, the implant helps with daily activities, such as locating objects and recognising large letters and shapes."In the patients that have been implanted to date, the improvement in the quality of life has been invaluable," said Mark Humayun of the University of Southern California's Keck School of Medicine and USC's Viterbi School of Engineering, who helped develop the device.

The Argus II was approved for use in Europe in 2011 and has been implanted in 30 patients in a clinical trial that began in 2007. In October, advisers to the FDA voted unanimously to approve the device.

According to the MIT Technology Review journal, the system costs about $115 000 (R1011 701) in Europe.The Argus II is intended to replace the function of light-sensing photoreceptor cells, which become degraded in retinitis pigmentosa. In people with retinitis pigmentosa, the light-sensitive cells slowly degenerate, resulting in gradual loss of side vision and night vision, and later of central vision.

FDA's approval of the device

The condition can lead to blindness.To restore vision, signals from the camera are sent to the retina, where they travel to the optic nerve in the brain. The brain then receives these signals and interprets them as a visual picture.The FDA approved the system as a humanitarian use device, an approval that is limited to fewer than 4 000 people in the United States each year.

For this kind of approval, companies must show the device is safe and the probable benefit outweighs the risks.In the clinical trial, most of the 30 participants improved in their ability to see and touch a square on a white field, detect the direction of a motion, recognise large letters and sentences, see street curbs and even match socks.

To receive the Argus II device, patients must have had the ability to see forms in the past and must be willing and able to get the recommended follow-up care and training.The device is limited to adults 25 or older, with severe to profound retinitis pigmentosa who have no light perception or bare light perception, in which they can perceive light but cannot tell where it is coming from.

The team plans to keep improving the treatment, which they hope will ultimately be used to treat age-related macular degeneration.
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